Bisulfite kinetics

The kinetics and mechanism of the ketone-bisulfite addition were studied by the use of the polarographic technique (Rao Salunke, Reaction Kinetics and Catalysis Letters 26 273, 1984).The specific rate was found to depend on pH. For an equimolar solution of bisulfite and acetone in a deaerated solution of potassium hydrogen phthalate buffer containing potassium iodide as the... 

Takeishi, et. al, have described the redox polymerization of methyl methacrylate in the absence of solvent (6). With 18-crown-6 as the phase transfer catalyst and potassium persulfate/sodiurn bisulfite as the redox couple, polymerization was observed at temperatures <50 C whereas little or no polymerization occurred under these conditions in the absence of bisulfite. Above 55 C, however, polymerization occurred even in the absence of bisulfite. From the limited kinetic data reported (6), one can estimate (13) that the rate of polymerization (Rp) is approximately proportional to the square root of crown concentration (Equation 1) ... 

In sulfite we have, apparently, a reducing agent which can function both as an oxygen acceptor and an electron acceptor and can serve as its own trap for these active Cr(IV) and Cr(V) intermediates. We have carried out the kinetics of this reaction at pH 5 in an acetate buffer, where, according to the literature, the species present in solution are HCrOf for the chromate and HSO3- for the bisulfite. The kinetics follow the stoichiometry... 

This difference in kinetics was exploited to develop a procedure to determine free and reversibly bound sulfite in food. The mobile phase consisted of an aqueous solution of 0.05 M tetra-butylammonium hydroxide adjusted to the desired pH by the addition of glacial acetic acid (34). Fluorimetric detection is also possible, because a reaction of the formaldehyde-bisulfite complex with 5-aminofluorescein gives a nonfluorescent product. The sulfite is measured indirectly by its suppresion of the fluorescence of the reagent (31). This method is applicable to the determination of S02 at > 10 ppm and is not applicable to dark-colored foods or ingredients where SO, is strongly bound, e.g., caramel color. This method does not detect naturally occurring sulfite. Sulfur dioxide is released by direct alkali extraction. 

The rates of nucleophilic additions to adamantanone have been studied in an attempt to determine the structure of the transition states of nucleophilic additions to carbonyl compounds in general. The kinetic analysis suggests that the transition states of borohydride reductions of ketones are product-like while for bisulfite additions the transition states are reactant-like 367). A similar analysis 36 ) of data obtained for photo-initiated oxetane formation (trans-dicyanoethylene + carbonyl compound) 3681 indicates a reactant-like transition state. 

The development of more efficient ferrous chelates that can increase the binding rate and equilibrium constant with NO, and also the reaction rate of ferrous nitrosyl chelates with sulfite/bisulfite ion, would allow the employment of smaller absorbers, reducing tanks, and L/G (flow rate ratio of scrubbing liquors to flue gas) to achieve the same scrubbing efficiencies. The determination of optimum scrubbing conditions and chemistry such that the formation of undesirable products can be depressed or eliminated would allow the reduction of cost in the area of scrubbing liquor regeneration. This paper addresses the kinetics and thermodynamics of important reactions in-... 

Recently, we have carried out studies on the free radical chemistry of sulfite. These studies have included kinetic measurements on the reactions of organic and inorganic free radicals with sulfite and bisulfite, and on the reactions of the sulfite derived radicals SO and S0 with organic and inorganic substrates. In this paper, I will review some of our results and results from other laboratories on the radical chemistry of sulfite and discuss these results in relation to the problem of S02 autoxidation. 

Flowing Clock" Modification of the Experiment. In conventional clock reactions, it is difficult to obtain reliable results for reaction times of less than 20 or 30 s. Since much of modem chemical kinetics is concerned with reactions occurring on much faster time scales, it is worthwhile to introduce a modification of such experiments that makes use of a simple flow system to explore reaction times of the order of a few seconds or less. Both the iodide oxidation and formaldehyde-bisulfite reactions can be investigated in this way. 

As pointed out by Skrabal and Schiffrer [173], the rate-determining step must be in the transition from acetal to hemiacetal because the rate coefficient for the hydrolysis of methyl ethyl formal is equal to the mean value of those for the hydrolyses of dimethyl formal and diethyl formal. Wolf and Hero Id [174] supplied more direct evidence on this matter. They found that the UV absorption bands of aldehydes slowly decrease in alcoholic solutions. This indicates that a reaction takes place. The product of the reaction immediately splits off aldehyde under the conditions of a bisulfite titration, therefore it cannot be acetal and it must be hemiacetal. Acetals are much more stable, and they are not hydrolyzed in a bisulfite titration. A quantitative kinetic study of the reaction of aldehyde with alcohol was carried out by Lauder (175] with the aid of dilatometric and refractive index measurements. He observed that hemiacetal is formed in a relatively fast reaction which is followed by a slow reaction leading to acetal. 

A review of the literature shows that photochemical reactions generally follow first-order kinetics. However, pseudo first-order, zero-order, and even fractional-order kinetics have been reported. Drugs reported to follow first-order kinetics include nifedipine (8) doxepin (41), riboflavin (28), minoxidil (48), adriamycin (52), doxorubicin, daunorubicin and epirubicin (61), folic acid (66), menadione sodium bisulfite (67), tetracycline hydrochloride (71), decarbazine (73), furosemide (74), democlocycline (76) and hydrocortisone, and prednisolone (90). Apparent pseudo first-order rate has been reported for pyridoxine (84). Indomethacin (91), sodium nalidixate (65), methotrexate (92), and metronidazole (68) have been reported... 

Bisulfite Addition Products and the Bucherer Reaction. The addition of sodium bisulfite to aldehydes and some ketones superficially appears to involve the addition of the elements Na and HS03 to the carbonyl group. Kinetic studies, however, indicate that the reaction is complicated and probably involves sulfite rather than bisulfite ion.10 One possible mechanism is the following ... 

From a theoretical point of view this is an extremely interesting reaction. The displacement of a hydroxyl group from a saturated carbon atom appears to be unknown in basic solution. The fact that amino-methane sulfonic acid can be isolated from the bisulfite addition product of formaldehyde on treatment with ammonia does not prove, of course, that a direct displacement, such as is indicated in XVI to XVII, actually occurred. Furthermore, it is quite clear that preliminary formation of an imine (XVIII) is not necessary for the reaction of aromatic amines with sodium bisulfite (steps XIX to XVIII to XVII, etc.). 1-Dimethyl-aminonaphthalene-4-sulfonic acid (XX) and l-aminonaphthalene-4-sulfonic acid (XIX) show similar reaction kinetics 16a when treated with sodium bisulfite, yet with the tertiary amine (XX) it is not possible to write an imino structure corresponding to XVIII. 

Carbonyl-bisulfite addition products are highly stable in aqueous solution at low pH, but they undergo facile dissociation under alkaline conditions. The kinetics of hydroxymethanesulfonate... 

Betterton, E. A., Y. Erel, and M. R. Hoffmann (1988), Aldehyde-Bisulfite Adducts Prediction of Some of Their Thermodynamic and Kinetic Properties, Environ. Technol. 22, 92-97. 

Finally, several equilibrium and kinetic properties of aldehyde-bisulfite adducts were found to be linearly related Taft s a parameter (Betterton et al.t 1988). These compounds, which include a-hydroxymethane sulfonate and other a-hydroxyalkyl sulfonates, may be important reservoirs of S(IV) species inj clouds, fog, and rain. Fairly good relationships were found between equilibrium properties (e.g. acidity constants) and Sir values, but rates constants for) nucleophilic addition of S03 to the aldehydes showed only a crude fit, Similarly, poor results were found in applying a to hydrolysis reactions of] volatile alkyl chlorides (T. Vogel, University of Michigan, personal communh cation, 1989), and this has been shown to be a general characteristic of reactioni of alkyl halides with nucleophiles (Okamoto et al., 1967). 

The rate of reaction between HSOj and O2 is shown to be much slower than the mass transfer rate and therefore is kinetically controlled. This rate, on analysis, is found to be 3/2 order in bisulfite concentration during a single experiment (Figure 3). 

The kinetic parameters of M AON401 were determined and used to optimize the rate of substrate-bisulfite addition over time to favor the productive sulfonation and limit buildup of the product imine which irreversibly inhibits the M AON401 (Scheme 18.15). 

In order to control the hi y exothermic polymerization reaction, the use of redox systems may be applied. The most commonly used system is posulfate, bisulfite and catalytic amounts of copper (or iron) ions, goKrating radicals by a chain reaction. This system has been studied in detail 1 Mfftk and Ugelstad [34]. The presence of trace impurities of metal ions in the reactants may be camouflaged by applying an excess of copper ions. The rate of radical production is in this case adjusted by addition of citrate (HCi ), which forms an inactive complex with Cu ions. Based on the observed kinetics, the following mechanism was postulated ... 

The kinetics of aqueous dispersion polymerization differ very little from acrylonitrile bulk or emulsion polymerization. Redox initiation is normally used in commercial production of polymers for acrylic fibers. This type of initiator can generate free radicals in an aqueous medium efficiently at relatively low temperatures. The most common redox system consists of ammonium or potassium persulfate (oxidizer), sodium bisulfite (reducing agent), and ferric or ferrous iron (catalyst). This system gives the added benefit of supplying dye sites for the fiber. 

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